TEHRAN (Reuters) -- Iran has arrested several people who were preparing to disrupt rallies on February 11 marking the 1979 Islamic revolution, police said today, in a clear warning to opposition supporters planning new protests.

Opposition leaders have called on people to take to the streets on February 11, raising the risk of renewed violence eight months after a disputed presidential election plunged the major oil producer into turmoil.

The authorities say the pro-reform opposition will face a firm response if it tries to hijack state-sponsored celebrations of the anniversary, when they say the Iranian nation in a display of unity will "punch the faces" of its Western enemies.

Events will be held across Iran, but the main official gathering will be at Tehran's Azadi square, where President Mahmud Ahmadinejad is expected to speak to a crowd which in previous years has numbered tens of thousands.

Opposition websites say the day belongs to all Iranians and have urged its backers to attend the rally, too.

"We are closely watching the activities of the sedition movement and several people who were preparing to disrupt the February 11 rallies were arrested," Fars News Agency quoted police chief Esmail Ahmadi-Moghaddam as saying, giving no details.

Referring to reports on the "sedition movement's plans" for the rallies, the official IRNA news agency quoted him as saying: "There will be no worries in this regard. We are fully prepared for holding a safe and glorious rally."

Suggesting the security forces would deploy in large numbers, he said police, the Revolutionary Guards and the Basij Islamic militia were "ready for any possible incident on February 11, and they will let no one create insecurity."

Embassy Protests

Some ordinary Iranians said they were apprehensive before the events marking the 31st anniversary of the revolution that toppled the U.S.-backed shah. "Many people are worried," one young academic said in Tehran, declining to be named.

Eight people were killed in clashes between the security forces and opposition supporters in late December, in the most serious bloodshed since the aftermath of the vote, when dozens died.

The opposition is showing no sign of backing down, despite many arrests in a continuing crackdown by the authorities.

Opposition leaders say the June election was rigged to secure Ahmadinejad's reelection.

Government officials have denied the charge and portrayed the huge protests that erupted after the poll as a foreign-backed bid to undermine the Islamic state, accusing Western governments of interfering in its internal affairs.

Hard-line students held demonstrations outside the French and Italian embassies on February 9.

After the June election, thousands of people protesting against the conduct of the vote were arrested.

Most of them have since been freed, though more than 80 people have been jailed for up to 15 years, including former senior government officials. A former deputy foreign minister was earlier this week sentenced to six years in jail.

Last month, Iran hanged two people sentenced to death in postvote trials. The West and human rights groups condemned the executions, accusing Iran of seeking to intimidate the opposition. On February 9, a court sentenced one of those detained during demonstrations on December 27 to death.